IMPACT OF THE MATURITY OF CORN FOR USE AS SILAGE IN THE DIETS OF DAIRY-COWS ON INTAKE, DIGESTION, AND MILK-PRODUCTION

Whole-plant corn was harvested at early dent, quarter milkline, two-th irds milkline, and black layer stages to evaluate the effects of matur ity on intake, digestion, and milk production when corn was fed as sil age in the diet. Twenty multiparous Holstein cows were used in a repli cated experiment with a 4 x 4 Latin square design with 28-d periods. D iets containing 50% forage (67% corn silage and 33% alfalfa silage) an d 50% concentrate (dry matter basis) were fed as total mixed rations. Moisture contents were 69.9, 67.6, 64.9, and 58.0% for silages from co rn harvested at early;dent, quarter milkline, two-thirds milkline, and black layer stages, respectively. Intakes of dry matter were similar across the four treatments and ranged from 3.73 to 3.79% of body weigh t. Milk production was highest (33.4 kg/d) for cows fed silage from co rn harvested at the two-thirds milkline stage and lowest (32.4 kg/d) f or cows fed silage from corn harvested at the early dent stage. Milk p rotein production was highest for cows fed silage from corn harvested at the two-thirds milkline stage (1.17 vs. 1.12 to 1.13 kg/d). Apparen t total tract digestion of dry matter, organic matter, crude protein, acid detergent fiber, and starch was lowest for cows fed silage from c orn harvested at the black layer stage. Although starch intake was sim ilar for cows fed silage from corn harvested at the two-thirds milklin e stage and for cows fed silage from corn harvested at the black layer stage (9 kg/d), intake of digestible starch was 0.4 kg/d lower for co ws fed silage from corn harvested at the black layer stage. The optimu m stage for corn that was ensiled was two-thirds milkline with some fl exibility between quarter and two-thirds milkline.